1. Field of the Invention
The present invention relates to a medical bladed device having a quadrangular pyramid shaped cutting blade portion formed thereto, and more particularly to a medical bladed device which provides excellent cutting performance during incision of living body tissue, inexpensiveness, and high endurance.
2. Description of Related Art
A medical bladed device has a function of forming a primary incision to a living body tissue by using a sharp tip portion thereof or by using a sharp cutting blade thereof, and has also a function of cutting open a living body tissue having a primary incision formed thereto by using a cutting blade thereof. The cutting performance of the medical bladed device is determined by the counterforce arisen during the forming of the primary incision and the counterforce arisen during the incising of the living body tissue.
More particularly, a medical bladed device having a cutting blade portion formed on a tip-side thereof with a quadrangular (e.g., rhombus shape) cross section is purposed for piercing, incising, or cutting off an extremely unsteady affected area with delicate manipulation of the finger tips by a careful operator, and has a sharp tip portion formed thereto, in which each side comprising the quadrangular shape is concentrated at the tip portion, thereby the sharp tip portion pierces a targeted living body tissue and a cutting blade extending from the tip portion passes through the living body tissue to: widen or cut off the targeted area.
Examples of the medical bladed device are a medical knife used in brain surgery, a medical knife used in ophthalmologic surgery for forming an incision by incising the cornea or a space between the cornea and the sclera, or a suture needle for suturing an incision. A good cutting performance, which includes a property of having little pierce counterforce when piercing a living body tissue and a property of having little incision counterforce when cutting open a living body tissue, and also rigidity (inflexibility), which is desired by physicians in handling a living body tissue are required for delicately manipulating the medical bladed device; in addition, other properties, such as excellent endurance against extensive repetitive use and inexpensiveness are also required.
Medical knives or suture needles, for example, used in ophthalmologic surgery have a tip portion being narrowly sharpened for enhancing piercing performance. However, narrowly sharpening the tip portion causes loss of endurance since the rigidity (inflexibility) of the tip portion decreases in association with narrowing and sharpening the tip portion. Furthermore, depending on the living body tissue, the tip portion will be unable to pierce if the tip portion is narrowly sharpened too excessively. Such problems prevents a physician from desirably performing an incising procedure, causes enormous stress for the physician, and may adversely affect proceeding of an operation.
When the cutting blade portion formed proximally to a tip-side has a quadrangular shaped cross section, a sharp peak, which has four sides (ridgelines forming the cutting blade and the back) matching at the tip, is required to be formed thereto for enhancing piercing performance. However, the process of matching the four sides at a single point causes increase in manufacture cost since device(s) for such process and product(s) are required to be controlled with extreme delicacy. Therefore, the tip portion, in actual circumstance, is corrected by hand after the tip portion and the cutting blade portion extending from the tip portion are processed.
The present applicant has already developed a technology relating to a suture needle capable of solving the aforementioned problems and has obtained a patent (Japanese Patent No. 1850827) thereof. This technology relates to a bladed suture needle having a three-faced tip portion, in which a quadrangular pyramid-like bladed suture needle has a three-faced tip portion consisted of two adjacent faces and one face formed by grinding or polishing two remaining faces of the quadrangular pyramid-like bladed suture needle. By forming the three-faced tip portion, the suture needle can have a triangle shaped cross section with the three faces constituting the triangle matched precisely at a peak portion for enabling excellent piercing performance.
In manufacturing the suture needle, two faces of a quadrangular pyramid-shaped portion are grinded or polished toward the remaining two sides of the quadrangular pyramid-shaped portion, so that a peak can be formed where each side is matched at the peak. This method is extremely simple compared to a method of polishing or grinding each four faces, so that a peak can be formed where four ridgelines formed between each face is matched at the peak. Accordingly, manufacture cost will not rise and a suture needle having excellent piercing performance can be provided.
An attempt of applying the same technology of the suture needle for manufacturing a medical bladed device (including a medical knife) based on the technology revealed some problems. That is, the medical bladed device being applied with such technology revealed a problem in manipulability owing to the shape of the three faced tip portion, wherein in some cases the medical bladed device can provide excellent manipulability with excellent cutting performance and high inflexibility, while in other cases the medical bladed device is unable to provide excellent cutting performance, or the medical bladed device, though being capable of providing satisfactory cutting performance, displays low inflexibility. That is, the medical bladed device revealed poor balance between cutting performance and inflexibility, lack of; consistency in performance, and difficulty in performing steady manipulation.
For example, piercing performance of the medical bladed device deteriorates and leads to a problem of poor cutting performance (including piercing performance) when the angle formed by two cutting blades among the three faces of the tip portion (cutting blade portion) become exceedingly larger than that of the cutting blades of the quadrangular pyramid shaped portion or when the three faced portion of the tip portion make up a large portion of the quadrangular pyramid shaped portion. Conversely, inflexibility decreases and leads to adverse results in manipulability when the angle formed by cutting blades of the tip portion become exceedingly small.
It is an object of the present invention to provide a medical bladed device for improving cutting performance and manipulability upon living body tissue and for improving endurance while preventing rise in manufacture cost.